Methods of forming a memory cell comprising a metal chalcogenide material

ABSTRACT

A method of forming a metal chalcogenide material. The method comprises introducing a metal precursor and a chalcogenide precursor into a chamber, and reacting the metal precursor and the chalcogenide precursor to form a metal chalcogenide material on a substrate. The metal precursor is a carboxylate of an alkali metal, an alkaline earth metal, a transition metal, a post-transition metal, or a metalloid. The chalcogenide precursor is a hydride, alkyl, or aryl precursor of sulfur, selenium, or tellurium or a silylhydride, silylalkyl, or silylaryl precursor of sulfur, selenium, or tellurium. Methods of forming a memory cell including the metal chalcogenide material are also disclosed, as are memory cells including the metal chalcogenide material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/333,774, filed Oct. 25, 2016, pending, which is a divisional of U.S.patent application Ser. No. 13/476,186, filed May 21, 2012, now, U.S.Pat. No. 9,496,491, issued Nov. 15, 2016, the disclosure of each whichis hereby incorporated herein in its entirety by this reference.

FIELD

The present disclosure, in various embodiments, relates generally to thefield of semiconductor device design and fabrication. More specifically,the present disclosure relates to a method of forming a metalchalcogenide material, and to methods of forming memory cells.

BACKGROUND

Over the past few decades, there has been interest in chalcogenidematerials for use in semiconductor devices, such as solar cells,photodetectors, or electroconductive electrodes. One such chalcogenidematerial is copper telluride (CuTe), which has been investigated for useas a cell material in conductive bridge random access memory (conductivebridge RAM) and phase change random access memory (PCRAM). One of thecurrent difficulties associated with CuTe is the deposition of thismaterial. CuTe is conventionally formed by a physical vapor deposition(PVD) or chemical vapor deposition (CVD) process, or by codeposition ofcopper and tellurium onto a surface within an evacuated chamber.However, due to the equipment and targets needed, these techniques areexpensive and take a considerable amount of time to become productionworthy.

Atomic layer deposition (ALD) of chalcogenide materials, such as certainmetal tellurides or certain metal selenides, has been investigated.Alkylsilyl tellurides and alkylsilyl selenides have been reacted withmetal halides to form metal tellurides or metal selenides, such as SbTe(Sb₂Te₃), GeTe, GeSbTe, ZnTe, BiTe (Bi₂Te₃), ZnSe, BiSe (Bi₂Se₃), InSe(In₂Se₃), or CuSe (Cu₂Se). Alkylsilyl selenides, such asbis(triethylsilyl) selenide, have also been reacted with copper(II)pivalate to form CuSe, Cu_(2-x)Se, and Cu₂Se. However, ALD processes forforming chalcogenide materials are limited by the availability,reactivity, and toxicity of appropriate ALD precursors.

It would be desirable to form additional chalcogenide materials, such asCuTe, by ALD processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an x-ray photoelectron spectroscopy (XPS) depth profile for ametal chalcogenide material formed by an embodiment of the presentdisclosure;

FIG. 2 is a scanning electron micrograph (SEM) of a metal chalcogenidematerial formed by an embodiment of the present disclosure;

FIG. 3 illustrates a partial cross-sectional view of an embodiment of amemory cell according to the present disclosure; and

FIGS. 4A-4D illustrate an embodiment of a method of forming a memorycell, such as the memory cell of FIG. 3.

DETAILED DESCRIPTION

Methods of forming a metal chalcogenide material by atomic layerdeposition (ALD) are described. As used herein, the terms “atomic layerdeposition” or “ALD” mean and include a vapor deposition process inwhich a plurality of separate deposition cycles are conducted in achamber. The term “atomic layer deposition,” as used herein, includes“atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE), gas sourceMBE, organometallic MBE, and chemical beam epitaxy when performed withalternating pulses of precursor compound(s) and purge (i.e., inert) gas.During each deposition cycle of the ALD process, a metal precursor ischemisorbed to a substrate surface, excess metal precursor is purged outof the chamber, a subsequent chalcogenide precursor is introduced toreact with the chemisorbed metal, and excess reaction gas and byproductsare removed from the chamber. By repeating the deposition and purgeacts, the metal chalcogenide material is formed by ALD.

The metal chalcogenide material formed by the ALD process may be acompound of the metal (i.e., an alkali metal, an alkaline earth metal, atransition metal, a post-transition metal, or a metalloid), and sulfur,selenium, or tellurium as the chalcogen. The metal chalcogenide materialmay include, but is not limited to, antimony sulfide (SbS), antimonyselenide (SbSe), germanium sulfide (GeS), germanium selenide (GeSe),zinc sulfide (ZnS), bismuth sulfide (BiS), indium sulfide (InS), indiumtelluride (InTe), copper sulfide (CuS), copper telluride (CuTe), silversulfide (AgS), silver selenide (AgSe), silver telluride (AgTe), goldsulfide (AuS), gold selenide (AuSe), or gold telluride (AuTe). In someembodiments, the metal chalcogenide material is CuTe. For convenienceand simplicity, the specific metal chalcogenide materials listed hereinindicate compounds that include the listed elements. The specific metalchalcogenide materials do not necessarily reflect the stoichiometry ofthe listed elements. Instead, the specific metal chalcogenide materialsmay be a stoichiometric or non-stoichiometric compound that includes thelisted elements. For example, the term “CuTe” indicates a stoichiometricor non-stoichiometric compound of copper and tellurium and may include,but is not limited to, CuTe, CuTe₄, Cu₂Te, Cu₄Te₃, Cu₇Te₄, or Cu₇Te₅.The metal chalcogenide material may, optionally, include additionalelement(s) as described below.

The metal chalcogenide material formed by some embodiments of thepresent disclosure does not include the following metal chalcogenidematerials: SbTe, GeTe, GeSbTe, ZnTe, BiTe, ZnSe, BiSe, InSe, and CuSe.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the present disclosure. However, a personof ordinary skill in the art would understand that the embodiments ofthe present disclosure may be practiced without employing these specificdetails. Indeed, the embodiments of the present disclosure may bepracticed in conjunction with conventional semiconductor fabricationtechniques employed in the industry. In addition, the descriptionprovided below does not form a complete process flow for manufacturing asemiconductor device. The semiconductor device structures describedbelow do not form a complete semiconductor device. Only those processacts and structures necessary to understand the embodiments of thepresent disclosure are described in detail below. Additional acts toform a complete semiconductor device from the semiconductor devicestructures may be performed by conventional fabrication techniques.

The illustrations presented herein are not meant to be actual views ofany particular semiconductor structure, but are merely idealizedrepresentations which are employed to describe the present invention.The figures are not necessarily drawn to scale. Additionally, elementscommon between figures may retain the same numerical designation.

The metal chalcogenide material may be formed by the ALD process on asurface of the substrate. As used herein, the term “substrate” means andincludes a base material or construction upon which additional materialsare formed. The substrate may be a semiconductor substrate, a basesemiconductor layer on a supporting structure, a metal electrode, or asemiconductor substrate having one or more materials, structures, orregions formed thereon. Previous process acts may have been conducted toform materials, regions, or junctions in the base semiconductorstructure or foundation. The substrate may be a conventional siliconsubstrate or other bulk substrate comprising a layer of semiconductivematerial. As used herein, the term “bulk substrate” means and includesnot only silicon wafers, but also silicon-on-insulator (SOI) substrates,such as silicon-on-sapphire (SOS) substrates and silicon-on-glass (SOG)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor or optoelectronic materials, such assilicon-germanium, germanium, gallium arsenide, gallium nitride, andindium phosphide. The substrate may be doped or undoped. By way ofexample, the substrate may be silicon, silicon dioxide, silicon withnative oxide, glass, semiconductor, metal oxide, metal, titanium nitride(TiN), a tantalum nitride (TaN_(x)), titanium (Ti), tantalum (Ta),niobium (Nb), a niobium nitride (NbN_(x)), a molybdenum nitride(MoN_(x)), molybdenum (Mo), a tungsten nitride (WN_(x)), copper (Cu),cobalt (Co), nickel (Ni), iron (Fe), aluminum (Al), or a noble metal.

The ALD process may be performed by conducting alternating pulses of themetal precursor and the chalcogenide precursor, with intervening pulsesof an inert gas. The inert gas may be nitrogen (N₂), argon (Ar), helium(He), neon (Ne), krypton (Kr), xenon (Xe), or other gases that, althoughnot inert, behave as inert under the conditions of the deposition of theprecursors. The metal precursor and the chalcogenide precursor mayfunction as a source of the metal and chalcogen, respectively, of themetal chalcogenide material. The metal and chalcogen, which are formedon the substrate, may be reacted to form the metal chalcogenidematerial. Each of the metal precursor and the chalcogenide precursor maybe solid, liquid, or gaseous at room temperature and atmosphericpressure. If the precursors are in a solid or liquid form at roomtemperature and atmospheric pressure, the precursors may be vaporizedbefore introduction into the chamber. Vaporization of the precursors maybe accomplished by conventional techniques, which are not described indetail herein. The precursors may be commercially available orsynthesized by conventional techniques.

The metal precursor may be an organometallic compound that includes acomplex of the metal and a ligand. The metal may be an alkali metal, analkaline earth metal, a transition metal, a post-transition metal, or ametalloid, such as antimony (Sb), bismuth (Bi), copper (Cu), gallium(Ga), germanium (Ge), gold (Au), indium (In), lead (Pb), nickel (Ni),palladium (Pd), silver (Ag), tin (Sn), or zinc (Zn). In someembodiments, the metal is copper. The ligand may be a carboxylate grouphaving the chemical formula R⁴C(O)O⁻, where R⁴ is an alkyl group havingless than or equal to eight carbon atoms. The R⁴ group may include, butis not limited to, a methyl, ethyl, propyl (n-propyl or iso-propyl),butyl (n-butyl, sec-butyl, iso-butyl, tent-butyl), pentyl, hexyl,heptyl, or octyl group. The ligand may include, but is not limited to,acetate, propionate, butyrate, isobutyrate, valerate, pivalate(trimethylacetate), or hexanoate. The ligand may also be a carboxylatesimilar to the pivalate group except in which one methyl group, twomethyl groups, or three methyl groups on the tertiary carbon arereplaced with one ethyl group, two ethyl groups, or three ethyl groups,respectively. In some embodiments, the ligand is pivalate. In someembodiments, the metal precursor is copper(II) pivalate.

The chalcogenide precursor may be a hydride precursor of the chalcogen,an alkyl precursor of the chalcogen, or an aryl precursor of thechalcogen, or a silylhydride precursor of the chalcogen, a silylalkylprecursor of the chalcogen, or a silylaryl precursor of the chalcogen,such as an alkyl precursor or a silylalkyl precursor of selenium or oftellurium. The chalcogenide precursor may have a chemical formula ofTe(R¹R²) or Se(R¹R²), where each of R¹and R² is independently hydrogen,an alkyl group having between two carbon atoms and four carbon atoms, oran aryl group. The alkyl group may be saturated or unsaturated and mayinclude heteroaroms, such as oxygen, nitrogen, or sulfur. Thus, each ofR¹ and R² may be an alkenyl, alkynyl, or alkoxide group. The aryl groupmay be a phenyl group, a substituted phenyl group, or aheteroatom-containing group, such as a nitrogen-containing group or asulfur-containing group. Each of R¹ and R² may be independently selectedso that the chalcogenide precursor exhibits desired properties, such asreactivity, volatility, and toxicity, for use in the ALD process. Thechalcogenide precursor may have a chemical formula of Te(SiR³R⁴R⁵)₂ orSe(SiR³R⁴R⁵)₂, where each of R³, R⁴, and R⁵ is independently hydrogen,an alkyl group having between one carbon atom and six carbon atoms, oran aryl group. The aryl group may be a phenyl group, a substitutedphenyl group, or a heteroatom-containing group, such as anitrogen-containing group or a sulfur-containing group. The alkyl groupmay be saturated or unsaturated and may include heteroaroms, such asoxygen, nitrogen, or sulfur. Thus, each of R³, R⁴, and R⁵ may be analkenyl, alkynyl, or alkoxide group. Each R³, R⁴, and R⁵ may beindependently selected so that the chalcogenide precursor exhibitsdesired properties, such as reactivity, volatility, and toxicity, foruse in the ALD process. The chalcogenide precursor and the metalprecursor may be selected to exhibit sufficient reactivity with oneanother to form the metal chalcogenide material on the substrate. Insome embodiments, the chalcogenide precursor is a bis(trialkylsilyl)telluride, such as bis(trimethylsilyl) telluride, bis(triethylsilyl)telluride, bis(diethylmethylsilyl) telluride, or bis(dimethylethylsilyl)telluride. In other embodiments, the chalcogenide precursor is a dialkyltelluride, such as diethyl telluride, diisopropyl telluride, dibutyltelluride, or bis(t-butyl) telluride.

Selection of the chalcogenide precursor may depend on the temperature atwhich the ALD process is to be conducted. By way of example, an alkylprecursor may be used when the ALD process is to be conducted at atemperature of from about 200° C. to about 325° C., while a silylalkylprecursor may be used when the ALD process is to be conducted at a lowertemperature, such as a temperature of from about room temperature (20°C.-25° C.) to about 275° C. In addition to reactivity and volatilityconsiderations, the temperature at which the ALD process is conductedmay depend on the thermal budget of a semiconductor structure in whichthe metal chalcogenide material is to be used. To prevent damage toother components of the semiconductor structure, the other componentsformed on or in the substrate should be compatible with the conditionsof the ALD process. By utilizing the hydride, alkyl, or aryl precursorof sulfur, selenium, or tellurium or the silylhydride, silylalkyl, orsilylaryl precursor of sulfur, selenium, or tellurium as thechalcogenide precursor, the ALD process for forming the metalchalcogenide material may be conducted across a wider temperature rangethan an ALD process utilizing conventional precursors.

While some alkyl precursors of selenium and tellurium have been used inconventional CVD processes, alkyl precursors of selenium or of telluriumhave not been used as precursors in ALD processes due to their reducedreactivity and concerns with toxicity. Therefore, the ability to usealkyl precursors of selenium or of tellurium in ALD processes of thepresent disclosure was unexpected.

To form the metal chalcogenide material, the precursors (i.e., the metalprecursor and the chalcogenide precursor) may be vaporized andsequentially deposited/chemisorbed to form a plurality of monolayers ofthe metal and the chalcogen on the substrate. Each monolayer of themetal and the chalcogen may be sequentially formed by separatelyintroducing the metal precursor and the chalcogenide precursor to anexposed surface of the substrate. To form the metal chalcogenidematerial, each of the precursors may be introduced to the substrateunder conditions that enable metal from the metal precursor or chalcogenfrom the chalcogenide precursor to chemisorb to the substrate, or toreact with metal or chalcogen previously chemisorbed on the substrate.Each of the metal of the metal precursor and the chalcogen of thechalcogenide precursor function as a reactant for the other andeliminate silicon-containing groups during the ALD process. Byappropriately selecting the reactivities of the metal precursor and thechalcogenide precursor, the ligand exchange reaction of the metalprecursor and the chalcogenide precursor is thermodynamically favorable,enabling formation of the metal chalcogenide material by an ALD processat a low temperature, such as at about room temperature. Since thereaction is thermodynamically favorable, the reaction may proceed tocompletion, which enables the metal chalcogenide material to be formedwith low amounts of impurities. The metal chalcogenide material may begreater than about 99% pure. Since the reaction is thermodynamicallyfavorable, the metal chalcogenide material may be formed without theaddition of heat, i.e., at room temperature.

To deposit the metal chalcogenide material on the substrate, a workpiece including the substrate may be placed into a chamber (or mayremain in the chamber from previous processing). The chamber may be aconventional ALD reactor, examples of which are known in the art and,therefore, are not described in detail herein. The metal precursor maybe introduced into the chamber and may chemisorb to a surface of thesubstrate. For the sake of simplicity, the precursors (i.e., the metalprecursor and the chalcogenide precursor) are described as being exposedto the substrate in a particular order. However, the precursors may beexposed to the substrate in any order. The metal precursor may be ofsufficient volatility and reactivity to adsorb onto or react with thesurface of the substrate. The metal precursor may be introduced into thechamber with the inert gas to form a mixture of the metal precursor andthe inert gas. The metal precursor may be introduced into the chamberfor an amount of time sufficient for the adsorption or reaction tooccur, such as from about 0.1 second to about 30 seconds. The metalprecursor may be introduced into the chamber at a flow rate of betweenabout 1 sccm and about 100 sccm, a temperature of between about 20° C.and about 400° C., and a pressure of between about 0.0005 Torr and about1 Torr. A monolayer of the metal may be formed on the surface of thesubstrate due to the chemisorption of the metal precursor on the surfaceof substrate. The monolayer formed by chemisorption of the metalprecursor may be self-terminated since a surface of the monolayer may benon-reactive with the metal precursor used in forming the monolayer.

Subsequent pulsing with the inert gas removes excess metal precursorfrom the chamber, specifically the metal precursor that has notchemisorbed to the surface of the substrate. Purging the chamber alsoremoves volatile by-products produced during the ALD process. The inertgas may be introduced into the chamber, for example, for from about 5seconds to about 120 seconds. After purging, the chamber may beevacuated, or “pumped,” to remove gases, such as excess precursor orvolatile by-products. For example, the metal precursor may be purgedfrom the chamber by techniques including, but not limited to, contactingthe substrate with the inert gas and/or lowering the pressure in thechamber to below the deposition pressure of the metal precursor toreduce the concentration of the metal precursor contacting the substrateand/or chemisorbed species. A suitable amount of purging to remove theexcess metal precursor and the volatile by-products may be determinedexperimentally, as known to those of ordinary skill in the art. The pumpand purge sequences may be repeated multiple times.

After purging, the chalcogenide precursor may be introduced into thechamber and may chemisorb to exposed surfaces of the monolayer of metal.The chalcogenide precursor may be of sufficient volatility andreactivity to adsorb onto or react with the metal. The chalcogenideprecursor may be introduced into the chamber for an amount of timesufficient for the adsorption or reaction to occur, such as from about0.1 second to about 30 seconds. For example, the chalcogenide precursormay be introduced into the chamber at a flow rate of between about 1sccm and about 100 sccm, a temperature of between about 20° C. and about400° C., and a pressure of between about 0.0005 Torr and about 1 Torr.Reaction byproducts and the excess chalcogenide precursor may be removedfrom the chamber utilizing the pump and purge cycle as described above.The chalcogen formation and purging may be repeated any number of timesto form a monolayer of chalcogen over the chemisorbed metal. Forexample, the chalcogen formation and purging may be repeated in sequencefrom about two times to about five times to form the monolayer ofchalcogen of a desired thickness.

The resulting metal chalcogenide material may be a glassy material thatincludes the metal and the chalcogen and in which the metal and thechalcogen are bonded to one another. The metal chalcogenide material maybe amorphous or crystalline as formed. By forming the metal chalcogenidematerial by ALD, the metal chalcogenide material may be formedconformally. In one embodiment, the metal chalcogenide material includesmicrosegregated areas of the metal and the chalcogen. In anotherembodiment, the metal chalcogenide material includes a greaterproportion of the metal relative to the chalcogen. Thus, the metalchalcogenide material may be characterized as “rich” in the metal. Theresulting metal chalcogenide material may have a high purity, with lowamounts of impurities, such as carbon and oxygen impurities. Theas-formed metal chalcogenide material may be substantially smooth,enabling the metal chalcogenide material to be deposited with excellentconformality.

A method of forming a metal chalcogenide material is disclosed, themethod comprising introducing a metal precursor and a chalcogenideprecursor into a chamber comprising a substrate. The metal precursorcomprises a carboxylate of an alkali metal, an alkaline earth metal, atransition metal, a post-transition metal, or a metalloid. Thechalcogenide precursor comprises a hydride, alkyl, or aryl precursor ofsulfur, selenium, or tellurium or a silylhydride, silylalkyl, orsilylaryl precursor of sulfur, selenium, or tellurium. The metalprecursor and the chalcogenide precursor are reacted to form a metalchalcogenide material. The metal chalcogenide material excludes SbTe,GeTe, GeSbTe, ZnTe, BiTe, ZnSe, BiSe, InSe, and CuSe.

In some embodiments, the metal chalcogenide material is CuTe, which isformed by using copper(II) pivalate and bis(trimethylsilyl) telluride asthe ALD precursors. During the ALD process, the copper(II) pivalate andbis(trimethylsilyl) telluride react with one another to form CuTe. Thereaction is thermodynamically favorable and enables a low depositiontemperature, such as room temperature, to be achieved. By forming theCuTe by ALD, the CuTe may be formed conformally.

A method of forming a metal chalcogenide material is disclosed, themethod comprising reacting copper(II) pivalate with a chalcogenideprecursor to form a copper telluride material on a substrate.

While the metal chalcogenide material has been described above as abinary compound, the metal chalcogenide materials may also be a ternaryor quaternary compound. The metal chalcogenide material may include atleast one additional element, such as another alkali metal, alkalineearth metal, transition metal, post-transition metal, or metalloid. Theadditional element may include, but is not limited to, Al, Sb, Bi,cadmium (Cd), chromium (Cr), Co, Cu, Ga, Ge, Au, hafnium (Hf), In, iron(Fe), Pb, manganese (Mn), mercury (Hg), Mo, Ni, Pd, platinum (Pt), Ag,Ta, Sn, Ti, tungsten (W), Zn, or zirconium (Zr). The additional elementmay also be a non-metal element(s), such as boron (B), nitrogen (N),oxygen (O), silicon (Si), phosphorus (P), or arsenic (As). Theadditional element(s) may affect the properties of the metalchalcogenide material, such as the ability to form the metalchalcogenide material in a crystalline form or an amorphous form. Theadditional element(s) may be selected to be compatible with the othermetal and chalcogen elements during the ALD process.

The metal chalcogenide material may be used as an ion source material ina memory cell, such as in a conductive bridge RAM cell. An embodiment ofa conductive bridge RAM cell 100 is illustrated in FIG. 3. Theconductive bridge RAM cell 100 includes a first electrode 102, adielectric material 103, a conductive material 105 disposed in at leastone opening 104 in the dielectric material 103, an active material 106,a ion source material 107, an insulator 108, and a second electrode 109.

The first electrode 102 may include a conductive material, such as, forexample, one or more of W, Ni, WN, TiN, TaN, polysilicon, and a metalsilicide (e.g., WSi_(x), TiSi_(x), CoSi_(x), TaSi_(x), MnSi_(x), where xis a rational number greater than zero). In some embodiments, the firstelectrode 102 may be a region of a semiconductor substrate doped so asto be electrically conductive. The first electrode 102 may be or be apart of a so-called “inert electrode” of a conductive bridge RAM cell.The dielectric material 103 may be positioned over the first electrode102 to isolate at least portions of the first electrode 102 from theactive material 106 positioned over the dielectric material 103. By wayof example and not limitation, the dielectric material 103 may includeat least one of silicon nitride (e.g., Si₃N₄) and silicon oxide (e.g.,SiO₂). The dielectric material 103 may be any dielectric materialconfigured to electrically isolate at least portions of the firstelectrode 102 from other materials formed over the dielectric material103. The dielectric material 103 may have the opening 104 in which theconductive material 105 may be disposed for providing electrical contactbetween the first electrode 102 and the active material 106. Theconductive material 105 may be the inert electrode contact of theconductive bridge RAM cell 100 and may include, by way of non-limitingexample, one or more of W, Ni, WN, TiN, TaN, polysilicon, a metalsilicide, etc.

The active material 106 may be positioned over the dielectric material103 and in electrical contact with the first electrode 102 through theconductive material 105. The active material 106 may be an oxidematerial (e.g., an oxide glass), such as at least one of a transitionmetal oxide (e.g., HfO_(x), ZrO_(x), WO_(x), etc.), a silicon oxide(e.g., SiO₂), an aluminum oxide (e.g., Al₂O₃), or a chalcogenidematerial (e.g., a chalcogenide glass). The chalcogenide material mayinclude at least one of the chalcogen elements, such as sulfur (S),selenium (Se), and tellurium (Te). The ion source material 107 may bepositioned over the active material 106 and may be electricallyconductive. The ion source material 107 may include an active metalspecies (e.g., Cu or Ag) for providing metal ions that drift (i.e.,diffuse) into the active material 106 upon application of a voltageacross the conductive bridge RAM cell 100 to form a conductive bridgethrough the active material 106. The conductive bridge may be removed(by applying a voltage with reversed polarity across the electrodes) ormay remain in place indefinitely without needing to be electricallyrefreshed or rewritten. The ion source material 107 may include themetal chalcogenide material and serves as the source of the Cu or Agions. In some embodiments, the ion source material 107 is CuTe. The ionsource material 107 may be formed over the active material 106 and aportion removed, such as by dry etching, followed by formation of theinsulator 108 adjacent to the ion source material 107. Alternatively,the insulator 108 may be formed over the active material 106 and anopening (not shown) formed therein. The opening may be filled with theion source material 107. The length of the ion source material 107 maybe the same as or greater than the length of the conductive material105. The second electrode 109 may be positioned over the ion sourcematerial 107 and the insulator 108. The second electrode 109 may beformed of an active metal, such as silver or copper, or may be formed ofa combination of a conductive ion source material and an inert metal capof, for example, tungsten, titanium nitride, or tantalum nitride.

A memory cell is disclosed, the memory cell comprising a dielectricmaterial over a first electrode, a conductive material in an opening inthe dielectric material, an active material over the conductive materialand the dielectric material, an ion source material conformally formedover the active material, and a second electrode over the ion sourcematerial. The ion source material comprises a metal chalcogenidematerial comprising Sb, Bi, Cu, Ga, Ge, Au, In, Pb, Ni, Pd, Ag, Sn, orZn as the metal and sulfur, selenium, or tellurium as the chalcogen. Themetal chalcogenide material excludes SbTe, GeTe, GeSbTe, ZnTe, BiTe,ZnSe, BiSe, InSe, and CuSe.

The conductive bridge RAM cell 100 may be formed by forming the firstelectrode 102 over or in a substrate (not shown), as shown in FIG. 4A.The formation of the first electrode 102 may be accomplished byconventional techniques and is, therefore, not described in detail inthe present disclosure. The dielectric material 103 may be formed overthe first electrode 102. The dielectric material 103 may be formed byconventional techniques and is, therefore, not described in detail inthe present disclosure. The opening 104 may be formed in the dielectricmaterial 103 by conventional methods (e.g., photolithography) and atleast partially filled with the conductive material 105 (e.g., TiN) toprovide electrical connection between the first electrode 102 and theactive material 106. The conductive material 105 may be formed in theopening 104 and planarized (e.g., by chemical mechanical planarization).

As shown in FIG. 4B, the active material 106 may be formed over thedielectric material 103 and the conductive material 105. The activematerial 106 may be configured to enable metal ions to move (i.e.,drift) therein responsive to a voltage applied across the activematerial 106. The active material 106 may be formed by conventionalmethods known in the art and, therefore, is not described herein indetail. By way of example and not limitation, the active material 106may be formed by at least one of PVD, CVD, and ALD techniques.

As shown in FIG. 4C, the ion source material 107 may be formed over theactive material 106. The ion source material 107 may be formed by ALD aspreviously described. Since an ALD process may be used to form the ionsource material 107, the ion source material 107 may be conformallydeposited over the active material 106. A portion of the ion sourcematerial 107 may be removed, such as by dry etching, followed byformation of the insulator 108 adjacent to the ion source material 107.Alternatively, the insulator 108 may be formed over the active material106 and an opening (not shown) formed therein. The opening may be filledwith the ion source material 107. The second electrode 109 may be formedover the ion source material 107 and insulator 108, as shown in FIG. 4D,producing conductive bridge RAM cell 100.

A method of forming a memory cell is disclosed, the method comprisingforming a dielectric material over a first electrode. A conductivematerial is formed in an opening in the dielectric material. An activematerial is formed over the conductive material and the dielectricmaterial. An ion source material is formed by atomic layer depositionover the active material. A second electrode is formed over the ionsource material.

By forming the metal chalcogenide material according to embodiments ofthe present disclosure, a highly conformal and pure metal chalcogenidematerial may be produced. The methods of the present disclosure enablethe formation of the metal chalcogenide material at a temperature at ornear room temperature. The memory cells including the metal chalcogenidematerial may be used in memory devices for wireless devices, personalcomputers, or other electronic devices.

The following example serves to explain embodiments of the presentinvention in more detail. This example is not to be construed as beingexhaustive or exclusive as to the scope of the disclosure.

EXAMPLE 1 ALD Process for Forming CuTe

CuTe was produced by an ALD process using copper(II) pivalate andbis(trimethylsilyl) telluride as the metal precursor and chalcogenideprecursor, respectively. Copper(II) pivalate were introduced into thechamber at a temperature of 200° C. After purging for 30 seconds,bis(trimethylsilyl) telluride was introduced at 1×10⁻³ Torr at atemperature of 200° C. The resulting material was analyzed by x-rayphotoelectron spectroscopy (XPS). The XPS depth profile for the CuTematerial is shown in FIG. 1, and demonstrates that the CuTe was highlypure, with carbon and oxygen impurities below detection limits. The CuTewas deposited as a substantially smooth material, as shown in FIG. 2.

The ALD process was conducted at various temperatures, ranging from roomtemperature to 250° C., i.e., at room temperature, 80° C., 125° C., 150°C., 200° C., and 250° C., to form the CuTe.

While Example 1 describes forming CuTe as the metal chalcogenidematerial, other metal chalcogenide materials may be formed in a similarmanner by appropriately selecting the metal precursor and thechalcogenide precursor.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the disclosure is not intended to be limited to the particularforms disclosed. Rather, the disclosure is to cover all modifications,equivalents, and alternatives falling within the scope of the followingappended claims and their legal equivalents.

1. A method of forming a memory cell, comprising: forming a dielectricmaterial over a first electrode, the dielectric material comprising atleast one opening therein; filling the at least one opening in thedielectric material with a conductive material; forming an activematerial over the conductive material and the dielectric material;conformally forming an ion source material over the active material, theion source material comprising a metal chalcogenide material comprisingantimony (Sb), bismuth (Bi), copper (Cu), gallium (Ga), germanium (Ge),gold (Au), indium (In), lead (Pb), nickel (Ni), palladium (Pd), silver(Ag), tin (Sn), or zinc (Zn) as the metal and sulfur, selenium, ortellurium as the chalcogen and the metal chalcogenide material excludingSbTe, GeTe, GeSbTe, ZnTe, BiTe, ZnSe, BiSe, InSe, and CuSe; and forminga second electrode over the ion source material.
 2. The method of claim1, wherein conformally forming an ion source material over the activematerial comprises conformally forming the metal chalcogenide materialcomprising a greater proportion of the metal relative to the chalcogen.3. The method of claim 1, wherein filling the at least one opening inthe dielectric material with a conductive material comprises forming theconductive material laterally adjacent to the dielectric material. 4.The method of claim 1, wherein forming an active material over theconductive material and the dielectric material comprises forming theactive material at a length substantially the same as a combined lengthof the conductive material and the dielectric material.
 5. The method ofclaim 1, wherein forming an active material over the conductive materialand the dielectric material comprises forming the active material at alength substantially the same as a length of the first electrode.
 6. Themethod of claim 1, wherein conformally forming an ion source materialover the active material comprises forming copper telluride by atomiclayer deposition over the active material.
 7. The method of claim 1,wherein conformally forming an ion source material over the activematerial comprises forming the ion source material at a lengthsubstantially the same as a length of the conductive material.
 8. Amethod of forming a memory cell, comprising forming a dielectricmaterial adjacent to a conductive material, the dielectric materialcomprising one or more openings therein; forming a contact in the one ormore openings in the dielectric material; forming an active materialadjacent to the contact and the dielectric material; forming an ionsource material adjacent to the active material by atomic layerdeposition; and forming another conductive material adjacent to the ionsource material.
 9. The method of claim 8, wherein forming a contact inthe one or more openings in the dielectric material comprises formingtungsten, nickel, tungsten nitride, titanium nitride, tantalum nitride,polysilicon, or a metal silicide in the one or more openings.
 10. Themethod of claim 8, wherein forming an ion source material adjacent tothe active material comprises forming the ion source material comprisinga metal chalcogenide material comprising antimony (Sb), bismuth (Bi),copper (Cu), gallium (Ga), germanium (Ge), gold (Au), indium (In), lead(Pb), nickel (Ni), palladium (Pd), silver (Ag), tin (Sn), or zinc (Zn)as the metal and sulfur, selenium, or tellurium as the chalcogen and themetal chalcogenide material excluding SbTe, GeTe, GeSbTe, ZnTe, BiTe,ZnSe, BiSe, InSe, and CuSe.
 11. The method of claim 8, wherein formingan ion source material adjacent to the active material comprises formingthe ion source material comprising copper or gold.
 12. The method ofclaim 8, wherein forming an ion source material adjacent to the activematerial comprises forming copper telluride adjacent to the activematerial.
 13. The method of claim 8, wherein forming an ion sourcematerial adjacent to the active material by atomic layer depositioncomprises reacting copper(II) pivalate with a tellurium precursor toform copper telluride adjacent to the active material.
 14. The method ofclaim 8, wherein forming an ion source material adjacent to the activematerial by atomic layer deposition comprises forming the ion sourcematerial to a length that is greater than or equal to a length of theconductive material.
 15. The method of claim 8, wherein forming anactive material adjacent to the contact and the dielectric materialcomprises forming the active material on exposed surfaces of the contactand the dielectric material.
 16. The method of claim 8, furthercomprising removing a portion of the ion source material before formingthe another conductive material adjacent to the ion source material. 17.A method of forming a memory cell, comprising forming a dielectricmaterial adjacent to a conductive material, the dielectric materialcomprising one or more openings therein; forming a contact in the one ormore openings in the dielectric material; forming an active materialdirectly over the contact and the dielectric material; forming an ionsource material by atomic layer deposition directly over the activematerial; and forming another conductive material adjacent to the ionsource material.
 18. The method of claim 17, wherein forming an ionsource material by atomic layer deposition comprises forming a metalchalcogenide material comprising copper telluride or gold telluride. 19.The method of claim 17, wherein forming an ion source material by atomiclayer deposition comprises forming a metal chalcogenide materialcomprising microsegregated areas of the metal and the chalcogen.
 20. Themethod of claim 17, wherein forming an ion source material by atomiclayer deposition comprises forming a metal chalcogenide materialcomprising a greater proportion of the metal relative to the chalcogen.